Function of Rubber membrane before the fuel Pump

[Seadoosam]

Hi all!
I was rebuilding my carbs and realized that the previous owner did not put the rubber membrane on before he put the fuel pump block. The ski was exhibiting the symptoms of slow to get to WOT and WOT was at only 6400 rpm and 42 mph.

Would this be the reason to blame? I didn’t see much else wrong or dirty with the carbs. I’m assuming that membrane is important (which I have now put on) but would it lead to those symptoms?

 

[JeremyD615]

I’m honestly not sure what it would do without it, but any carb problems are a big deal on these things. Water test it and see if the missing revs are back... Be sure to let us know how it turns out so we have a resolution to the thread too!

 

[Seadoosam]

I’m honestly not sure what it would do without it, but any carb problems are a big deal on these things. Water test it and see if the missing revs are back... Be sure to let us know how it turns out so we have a resolution to the thread too!

will do. testing tomorrow hopefully

 

[etemplet]

Check your water control valve for leaking. Check your engine compression.

As for the Carb, I'm not sure what that thin rubber thing does other than helps the o-ring gasket seal better. Give that is not in it's proper place I'd suspect other issues with the carbs. Go through the Carb Thread. I'd suggest looking at the 3 holes in the barrel and the 4th for good flow. Insure your jets and seats are the correct size. Verify everything. Good LUck.